1. Field of the Invention
The present invention relates generally to integrated circuits having secured information stored within and, more specifically, relates to a security circuit for controlling access attempts to the secured information within the integrated circuit.
2. Discussion of Related Art
Many computing applications are commonly referred to as embedded computing applications wherein a general or special purpose processor or custom processing circuits perform a particular application embedded within the end user device or system. An end user of such an embedded system or device has little or no direct interaction with the programmed instructions or sequences of operations but rather is limited to the intended user interface features of the embedded system. Such embedded systems are ubiquitous in the present day including simple consumer devices such as telephones and household appliances as well as a variety of commercial applications including telecommunications, special purpose computing, office equipment, etc.
Many such embedded applications include information that is intended to be secured from unauthorized access. For example, the manufacturer of an embedded application device may wish to preclude any direct end user access to particular sensitive data or to the programmed instructions and data within the embedded application device. For example, security IDs or passwords stored within the embedded device may require such security from unauthorized access. Or, for example, the very code itself that operates the embedded system or device may be secured from unauthorized access to prevent unauthorized copying, reverse engineering or modification of the data and/or program instructions of the embedded system or device.
Frequently such secured embedded applications may utilize flash memory or other non-volatile programmable memory devices to store the secured information. To further enhance the security, the flash memory is often embedded and integrated with the general or special purpose processor or other processing circuits specific to the application. Further, to reduce cost and complexity of such embedded flash memories, numerous manufacturers are applying so-called Known Good Die Flash—a flash memory external to the processing circuits but intended to be packaged within the same integrated circuit. Such a flash memory may be stacked or tightly coupled to other circuit features of the embedded system integrated circuit package. Often such integration is referred to as System On a Chip or (“SOC”).
Although the integrated circuit package may physically enclose such a flash memory device, hackers and thieves may exploit external pins associated with the integrated circuit to extract secured information from the flash memory circuits embedded within the SOC integrated circuit. To enhance the security of such information in a memory within the SOC integrated circuit, prior approaches have applied encryption techniques to the secured data. Thus, though a hacker or thief may find ways to exploit the external pins of the SOC integrated circuit to extract the secured data, the secured data will still be encrypted and hopefully, thereby remain secured though successfully accessed.
However, such encryption techniques give rise to numerous complexities that affect both cost and performance of the SOC integrated circuit. For example, during normal utilization of the secured information additional latencies may be incurred to provide the requisite decryption of the encrypted secured data. Further, a significant number of additional logic gates and circuits may be required to implement the required decryption of the secured information. Still further, when utilizing such encryption, it may be desirable to periodically modify the encryption key and re-record the encrypted secured information with an updated encryption key. However, an embedded device is often devoid of any external network access to allow such encryption key modifications associated with well-known public key encryption techniques.
It is evident from the above discussion that a need exists for improved security methods and structures for secured information embedded within an embedded system or device SOC integrated circuit.